Biological sources

These energy sources are all carbon dioxide neutral. Growing
vegetation absorbs carbon dioxide from the atmosphere and burning
the biomass for energy returns it to the atmosphere. Looked at in
this light, the various "forestry carbon dioxide sequestration
schemes" cannot affect the growing amount of that gas in the
atmosphere in the long term. Sure, the forest will absorb carbon
dioxide as it grows and matures. However, the ultimate fate of
every tree in that forest is one of the following:

The forest catches fire.

The trees die, fall down and rot.

The trees are logged, turned into houses, paper or
furniture and eventually burnt or sent to a dump to rot.

There are no other possibilities. All these outcomes put the
carbon dioxide back in the atmosphere. Result: its another
zero-sum game as far as atmospheric carbon dioxide is concerned
and anybody who tells you different is either fraudulent, a liar
or both.

The United Kingdom probably cannot feed its current population
without importing food, so horse-drawn transport is impossible
here without a return to 19th century population and city sizes.
The USA does not have the farmland to feed its required horses
and has not had this capability since the late 1960s. Thats even
assuming that farms are not needed to feed people. Now knock off
all the areas that require major pumped irrigation and other
energy inputs for farming or for people to live there: much of
the Californian farmland, virtually everybody living in Arizona,
Nevada and the Columbia Valley. None of these are killer problems
but they can still cause major upheavals, like mass resettlement
of the Las Vegas blue-rinses and/or another Dust Bowl.

Biofuel is a general term for the biological production of
liquid fuels which will be burnt in conventional engines or
heating systems.

Growing plants absorb carbon dioxide, which is returned to the
atmosphere when the biofuel is burnt, so biofuel use is carbon
neutral. Biofuel production is also carbon dioxide neutral
provided that biofuel and the associated waste biomass supplies
all the required energy for farm machinery and agrochemical
production, crop cultivation, harvesting and converting biomass
into fuel.

Overall conversion efficiency is important because it governs
the amount of land needed to produce a given amount of fuel. This
is almost certainly the limiting factor for biofuel production on
land.

Algal biofuel

An alternative is offered by algae. This is pond scum, rich in
lipids or starches, so it provides potential sources of biodiesel
or bioethanol respectively. Efficiency should be comparable to
systems that convert entire plants to fuel. Additionally, algae
can be grown on brackish ponds, in seawater or in enclosed
systems installed on deserts. This potentially sidesteps
production limits due to available farmland and fresh water,
which is either in the sea or recycled within an enclosed system.
However, its far from clear that algal systems can avoid either
diverting fertiliser from conventional farming or boosting
fertiliser production to unsustainable levels. Another drawback
is that wild microbes and algae tend to contaminate open ponds
and consume the oil producing algae and/or reduce the yield.
Solutions are:

Use closed reactors, but these are expensive and require
careful maintenance and cleaning.

Use a hybrid system: grow a large number of small algae in
closed bioreactors and transfer them to outside ponds to
rapidly gain mass for harvesting before contaminating organisms
have time to infiltrate the pond.

Bio Fuel Systems
(BFS), a Spanish startup in Alicante, is using cyanobacteria
and sunlight to convert carbon dioxide from a cement works into
crude oil via a patented system using heat and pressure. It
claims this process is carbon negative because,
after oil extraction, a lot of the waste is in the form of a
carbonate sludge that can be buried or used to make concrete. The
carbon negative claim arises because the inputs needed to make a
barrel of oil (159 litres) are 2000 kg of flue-gas carbon dioxide
and 226 kg of fuel to provide the heat (producing 700 kg of
carbon dioxide in the process). Burning the resulting oil
produces another 450 kg of carbon dioxide. This leaves 850 kg of
carbon-dioxide permanently trapped in the solid residue: hence
the carbon negative claim. In theory, if this system was scaled
up to produce 90 million barrels of oil a day (the world's crude
oil consumption in 2012), thus replacing all oil extraction, it
would occupy just 25% of the Libyan desert, or 1% of the global
pasture land. However, it produces rather expensive oil: the
estimated cost is at least $US5 (£3.10) a litre. This is
mostly due to the cost of the polycarbonate reactors and the
electricity needed to stir them. These figures are extrapolated
from a pilot plant that produces about 2.5 barrels of oil a day.
- New Scientist, 8
December 2012, page 36.

Algae Systems, an
American startup, would bypass this by using 25 metre plastic
bags floating just offshore in the ocean where wave action
provides the necessary stirring. A pilot plant should be
operational in 2013. It should be carbon negative because its
algal processing methods will be similar to thise used by BFS.
However, they point out that a major limit to using algae is the
expense and limited sources of available nitrogen and phosphorus
fertilisers. Calculations show that the entire US supply of these
fertilisers would enable less than 10% of the US liquid fuel
demand. Available carbon dioxide from American smokestacks set a
similar limit. - New
Scientist, 8 December 2012, page 36.

Biodiesel

Oil producing crops, such as rape seed or soybeans, are grown
using normal arable farming methods. The oil is extracted and
converted into biodiesel which can be used to power diesel
engines or heating systems.

Ethanol

This is produced by growing sugar-producing crops, such as
sugar-cane, sugar-beet or maize, extracting the sugar and
fermenting it into ethanol which is used to fuel internal
combustion engines.

Around 2005 Iogen
demonstrated a process for producing
fuel-grade ethanol from arable crop waste biomaterials. The
improvements are, firstly, treating the raw materials to increase
the surface area of the plant fibres before using enzymatic
hydrolysis to convert much of the cellulose to glucose. This is
separated and fermented while the solids are burnt to power the
process.

Bruce Dale (Office of Biobased Technologies at Michigan
State University in East Lansing) announced the development of
the AFEX (Ammonia Fibre EXpansion) process which increases
plant fibre area by heating the plant material to 100°C at
20 bar in an ammonia atmosphere for 5 minutes. This is followed
by explosive decompression, followed by enzymatic conversion of
the cellulose to sugar, which is then yeast or bacterial
fermentation to produce ethanol. It is claimed that this
process can convert 90% of the cellulose into biofuel, which is
said to be 188% better than previous systems. Plant material
averages 33% cellulose, so the claimed output of 300 litres of
ethanol per tonne of plant material equates to 73% maximum
theoretical yield - not exactly 90% conversion, is it! Once you
look at likely plant efficiency I'd be surprised if this
process is much better than those it aims to replace.

ZeaChem of Lakewood,
Colorado claims it can get 500 litres of ethanol per tonne of
plant waste. After converting the cellulose to xylose and
glucose by a thermochemical fractionation process, the sugars
are converted to acetic acid by bacterial fermentation.
Meanwhile lignin, another output of the fractionation process,
is gasified to produce a hydrogen-rich syngas stream. The
acetic acid is esterified and the result hydrogenated to
produce ethanol. The rest of the syngas is used to power the
process.

Microbiogen, an
Australian firm in Lane Cove, NSW, uses a frementation process.
After breaking down the hemicellulose and celluloser in plant
cell walls xylose and cellulose. This mixture is fermented to
ethanol with a specially developed, non-GM, strain of yeast,
which can be used for animal and human food production. Yield
is 200 litres of ethanol plus 80-90 kg of high protein yeast
per tonne of plant material.

Waste biomass

Cool Planet Energy
Systems think pyrolytic decomposition of waste plant biomass,
i.e. straw, corn harvest waste and forestry waste wood, offers a
cheaper and more sustainable solution. In their system, pyrolysis
converts waste plant biomass into hydrocarbon fuel and biochar.
The hydrocarbons can be used as fuel with little further
processing while the biochar can be used as a soil improver or
buried permanently. The last choice makes the process carbon
negative because up to half the carbon it processes gets buried
as biochar: the rest would be returned to the atmosphere. Ideally
the system would be deployed as several hundred small units. This
would minimise transport costs by collecting waste biomass within
a radius of 50km or so and supplying fuel over a similar area.
They estimate that, if biochar contains 33% of the carbon input
to the process, they can produce fuel for about $US0.40
(£0.25) a litre. - New Scientist, 8 December 2012,
page 37.

Is biofuel viable?

A study by David Tilman and colleagues at the University of
Minnesota in St. Paul (Proceedings of the National Academy of
Sciences, DOI: 10.1073/pnas.0604600103) says probably not.
They calculate the result of America turning all its maize and
soybean production into biofuel. They further assume that some of
this biofuel will be used to manufacture the farm machinery,
fertiliser and pesticides needed to grow the crops and to run the
machinery used to cultivate and harvest it. The remaining biofuel
would meet less than 5% of America's current liquid fuel
requirement. As of 2010 this approach to ethanol production is
pretty much a dead duck thanks to its impact on food
production.

Its clear that ethanol production isn't particularly
efficient:

The energy inputs, in the form of fertilisers, cultivation and
harvesting are considerable. Studies have put these inputs at
anything from 75% to over 100% of the energy content of the
resulting ethanol.
- Congressional Record page H211, Congressman Roscoe
Bartlett: "THE PEAKING OF WORLD OIL", House of Representatives,
February 8, 2006,
http://www.peakoil.net/Publications/PeakOilSpclOrder%2315TextCharts020806Low.pdf.

Its not clear what proportion of this added energy is derived
from burning the biowaste that's left after the sugar has been
extracted and how much is obtained from fossil fuel.

In terms of an energy balance, or on a "comprehensive life
cycle basis," ethanol contains about twice the amount of energy
required to produce it. This includes the energy used to
produce the various inputs of production such as fertilizer and
pesticides, the fuel costs associated with grain production,
and the cost of transporting grain from the farm to the ethanol
plant, and from the ethanol plant to the retailer.
- Agriculture Canada

A study in 2006, by Alex Farrell from the University of
California at Berkley, calculated that ethanol made from maize
releases only 25% more energy than is required to grow the crop
once the large amount of fertiliser it requires is taken into
account. This is because making fertiliser is very
energy-intensive. In addition, runoff from the fields pollutes
streams and creates dead zones as the resulting blooms mop up
dissolved oxygen. Growing corn to produce ethanol is not a
good idea.

Producing ethanol by fermenting cellulose looked initially as
if it could be worthwhile. The base crop is wild grasses that are
native to the growing area. Unlike maize, the whole plant is
harvested and fermented, vastly improving the efficiency of the
process. The yields from farm-scale experiments run by Robert
Mitchell, who is based at the University of Nebraska, combined
with ethanol production models show that this system should
produce up to 93% more energy than is used by growing and
processing the grass if fertiliser is used. Jason Hill,
University of Minnesota, did a similar experiment but without
using fertiliser and got energy yields in the range of 60% to
85%, still much better than maize. When he tried grass mixtures
in place of monocultures the energy yield improved by 150% to
238%. Added benefits of this approach are the avoidance of a
monoculture, minimal harm to wildlife (the annual harvest has a
similar effect to the annual grass fires that affect prairies)
and minimal pollution. However, two reports in Science
(February, 2008 issue) say that this, still hypothetical, process
will always have negative consequences regardless of the overall
energy production efficiency. If cropland is used it will
adversely affect food supplies regardless of its implementation.
If uncultivated land is used, the effect of carbon release from
this area combined with the loss of future biological carbon
sequestration will result in a nett increase in carbon emissions.
More details are available in
US scientists puncture the ethanol biofuel bubble, an
analysis published in The
Register. It seems that cellulose fermentation is probably
just another bad idea.

Some studies have shown that British arable farming has more
energy input in the form of fertilizers, cultivation and
harvesting than it gets from the sun, so producing biofuel in the
UK may turn out to be an energy sink rather than a resource.

No efficiency estimates have been released for algal systems.
In theory they could be better than converting land plants -
providing that preparing the biomass for processing needs less
energy than harvesting crops. The jury is still out on algae.

George Monbiot pointed
out (Feeding
cars, not people, 23/11/2004) that using rapeseed oil to run
UK's road transport on biodiesel requires 25.9m hectares of farm
land. Unfortunately, there is only 5.7m hectares of farmland in
the UK. He thinks production will inevitably switch to Indonesian
and Malaysian palm oil, causing widespread deforestation and
starvation because British drivers will pay more for petrol than
local people can afford to pay for food. An update of this survey
(
An agricultural crime against humanity, 06/11/2007) pointed
out that governments are using biofuel as a way of avoiding hard
decisions and ignoring the harm it does.

In fact the situation is far worse than George Monbiot foresaw
in his worst nightmare. Indonesian speculators are clear felling
rain forest as fast as they can in order to plant oil palms. The
carbon this is releasing from the underlying peat swamps is
currently adding an extra 10% to atmospheric emissions from
fossil fuel - New
Scientist, 1 December 2007, page 50.

Other calculations (New
Scientist, 15 December 2007, page 6) show that large scale
biofuel production is unsustainable because there simply isn't
enough agricultural land or water to support it. Here are two
estimates from that article:

To replace 7.5% of current petrol use (140 billion litres)
needs an extra 280 km^3 of water and at least 30 million
hectares of land. The effect of improved crop yields has been
factored into these estimates. (Charlotte de Fraiture,
International Water Management Institute, Columbo, Sri
Lanka)

There is only 250-300 million hectares of unused but
suitable land for biofuel production in the world. Even using
the most efficient cellulose conversion systems, 290 million
hectares would be needed to meet just 10% of the world's energy
demand by 2030. However, by then, 200 million hectares of that
land will be needed to feed the extra 2-3 billion people who
will have been born by then. (Sten Nilsson, International
Institute for Applied Systems Analysis, Laxenburg, Austria)
On top of this an extra 540 to 1600 km^3 of water per year will
be needed. To put this in perspective, the world's total annual
river flow is 14,000 km^3: biofuel production would increase
water consumption by somewhere between 4% and 11% of all the
available fresh water. This was scaled from a calculation of
the water needed for enough biofuel to replace 50% of the
fossil fuels used for electricity generation and transport in
2050. (Johan Rockstrom, Stockholm Environment Institute,
Sweden). I took 20% of Rockstrom's estimate and scaled the
energy requirement to 2030 by assuming a 2% annual increase in
energy demand.

This view is supported by more recent American statistics for
ethanol production. In 2010 ethanol production from corn provided
8% of the fuel used by transport, consuming nearly 40% of the
American corn crop in the process (New Scientist, 8 December 2012,
page 35). The bottom line is that ethanol from this source can't
provide more than 20% of the US demand for transport fuel if we
assume that all the land thats suitable for growing corn already
does so. Bear in mind that the damage this would do to food
production is ignored and that it has no impact whatsoever on
fossil fuels consumed by electricity production, used in industry
and for heating.

Even though the assumptions, and hence estimates of land and
water requirements differ quite widely I think they show that a
biofuelled world is simply a nonstarter once the impact of the
world's still expanding population is taken into account. Water
seems to be the limiting factor rather than agricultural land: de
Fraiture's figures show that it requires 2000 litres of water to
produce each litre of biofuel.

An analysis (New
Scientist, 16 August 2008, page 34) of the feasibility of
using biofuel for aviation supports this view. At the time the
article was written aviation consumed around 238 million tonnes
of jet fuel a year. The analysis looked at the land required to
produce this amount of fuel without impacting food
production:

Jatropha curcas nuts. This tropical bush grows on
poor land with little or no water and fertiliser requirements.
As a result it is claimed that using it for biofuel would not
affect agriculture. It yields 1.7 tonnes of oil per hectare, so
would need 1.4 million sq.km of land to grow the current jet
fuel requirement. Thats about twice the area of France.

It is claimed that about 2 tonnes/hectare of oil can be
made from waste biomass that can be collected without impacting
either forestry or agriculture. The source biomass is waste
lumber, straw, maize stalks, etc. This can be processed to jet
fuel using the Fischer-Tropsch process but, as this is energy
intensive, a significant amount of the biomass would be used to
power the fuel synthesis. As a result this too would need a lot
of land to meet the fuel requirement. This is estimated to be
1.2 million sq.km, or three times the area of Germany.

Algal production is the remaining hope, and is the only one
of these methods to have a track record of pilot plant
production. Seambiotic
have a plant near Ashkelon, Israel. It uses ponds fed with warm
water from a coal-fired power station to grow algae, feeds them
with carbon dioxide from scrubbed flue gas and operates the
extraction with cheap energy from the power station. Practical
experience over twenty years shows the yield to be about 36
tonnes of oil per hectare. Even though this is much better than
the other two methods, it still adds up to 66,000 sq.km, an
area about the size of Ireland., to produce the required jet
fuel.

Given the vast amount of land needed for any of these
approaches its difficult to see how this can avoid an
agricultural impact, although algal production could at least
take place on desert bordering the sea. However, this analysis
has ignored any growth in air traffic and it skips over possible
fertiliser requirements. These may be needed to replace the plant
nutrients that normal cropping would plough back into the land as
straw and stalks.

Does biofuel reduce carbon emissions?

Not so's you'd notice. A study by Joseph Fargione and
colleagues at the Nature Conservancy, Minneapolis, MN looked at
the carbon debt incurred by clearing land for biodiesel
production. The carbon debt from clearing Brazillian rain forest
to make fuel from soya beans would take 300 years to recoup by
reduced carbon emissions. Clearing Indonesian rain forest to
produce fuel from palm oil would take 400 years to show a net
carbon reduction. - reported in New Scientist, 16 Feb 2008,
page 19.

Algal biofuel production should be better in this respect,
simply because there is no land clearance involved. There's only
the carbon cost of building a tank system off the coast or an
enclosed system in a desert and of the associated fuel production
facility.

Knock-on effects

If you grow biofuel you'll have to find the land somewhere.
You have just three choices: do without the previous produce,
displace previous production to new land or grow the biofuel on
new land. Doing without is a non-starter due to its impact on
food availability and price. Both the other options require new
land to be brought into production by clearing forests, draining
swamps, etc. This will certainly damage wildlife and may have
additional unforseen ecological effects. It will certainly boost
carbon emissions: see above.

Biofuel-powered thermal generation

Plantations of fast-growing trees, such as willows, are
coppiced and burnt in power plants near or in the plantations.
Solid plant waste from ethanol or biodiesel plantations is also
suitable fuel for electricity generation. The ash should probably
be returned to the plantations as fertiliser.

Judging by the rate that North American forests are vanishing
there is no spare capacity there for energy generation, renewable
or not. From what I heard and saw back in 1991 on the Olympic
Peninsular near Seattle in Washington State, the forestry
companies are making no attempt to replant what they cut. Rape
and pillage seems to be the name of that game. Besides, even if
there was replanting, the great northern forests in the USA and
Canada are very slow growing. I have been quoted 150 years as the
expected regeneration time.

United Kingdom forests are more or less static and trees are
pretty slow growing here too, so electricity generation from wood
is unlikely to have much impact on the demand for energy.

New Zealand has extensive exotic forests for the paper pulp
export trade. The Mediterranean pine, pinus radiata, grows very
fast on the volcanic plateau near Rotorua. In the early 1970s,
when forest planting had been completed and the trees had matured
enough for harvesting, the Kaingaroa Forest provided a
sustainable harvest of 8000 tonnes of wood a day. If the export
trade for the resulting newsprint is reduced by the oil crisis,
the output of this forest could fairly easily be diverted to
sustainable electricity generation.

Photosynthetic Microbial Fuel Cells

Some interesting work is being done in Holland on direct
electricity production by growing plants. This relies on the fact
that a significant proportion of the sugars and proteins
synthesised by green plants leaks out into the soil from their
roots where they are metabolised by bacteria, which in turn
release electrons. The electricity is harvested by wiring the
soil the plants are growing in so it forms a microbial fuel cell.
Given suitable development, the researchers expect that an output
of 3.2 W/m2 is possible under laboratory conditions
while an outdoor system, based on marsh grasses growing in
waterlogged soil, might realistically yield 1.6 W/m2.
It has a big advantage over solar power because it will continue
to provide electricity after dark.

Comparisons with other renewables are interesting. For the
same annual electricity output, this type of PMFS requires five
times the land area that wind farms or PV solar generators would
occupy. However, to get the same electricity output from growing
biofuel and using it to generate electricity would need 35 times
the land area required by a PMFS system.

Research, reported in New Scientist (25 Feb 2006,
p37), has demonstrated direct hydrogen production by the green
alga Chlamydomonas reinhardtii. The idea is to grow the
algae in transparent, water-filled polythene tubes. Supply the
algae with nutrients and sunlight and they produce hydrogen and
oxygen. Then you remove the gas mixture from the array of tubes,
separate and dry the hydrogen and ship it off to be used as
fuel.

Water use should be minimal because it would be recycled. The
impact on arable land should also be tiny because because this
type of hydrogen farm can be installed in empty desert.

Its been calculated that enough hydrogen could be produced to
replace all the petrol used in the USA by 25,000 sq.km of
hydrogen farms given a solar conversion efficiency of 10%. To put
this in perspective, this is a tenth of the area that American
farmers currently use to grow soya beans. That's 0.3% of the land
area the USA or 8.4% of Arizona. If it works, it could provide an
income source to developing countries by allowing the Middle East
and North Africa to supply Eurasia with hydrogen.

The snag is that the current conversion efficiency is under
0.1%, so some serious genetic engineering is needed before this
becomes a viable energy source.

Biological conclusion

It has been estimated that the human ecological impact already
exceeds the sustainable capacity of the globe. We are approaching
and even exceeding the sustainable fresh water supply in many
parts of the world. Both these factors are likely to severely
limit biological energy sources.

With the possible exception of biogenic hydrogen, scratch the
biological options without a severe dose of human
depopulation.